Intake manifold gasket
I would say yes, if oil has mixed with the coolant, that's the most probable cause.
is coolant leaking from engine?or is it leaking from water pump and running down engine and appears to leak from engine
Your coolant pump is behined the fan, you will have to replace the water pump.
It is possible for engine oil to float on engine coolant. This occurs when there is a leaking or blown gasket.
There is a heater hose that goes to the left rear top side of the intake manifold and that fitting leaks engine coolant sometimes and it will run down the back of the intake around the distributor. If that fitting is not leaking then the intake manifold gasket is leaking coolant in the corners of it. REplace the intake gasket. That's all that can leak coolant on that year engine. If coolant is leaking out between the transmission and engine block then you have a freeze plug leaking in the back of the engine, between the transmission and block. Must remove the transmission and flywheel to fix it.
this is usually engine coolant leaking in
you might have a blown head gasket and the coolant is leaking into the cylender and the engine is burning it.
The head gasket sits between the head and the engine block if it is leaking out where you can see the coolant, yes you can smell the coolant if it is leaking into the engine no you cannot smell the coolant. You can check the oil to see if it has coolant in the oil if it does then the head gasket might be blown.
Your engine may have a leaking hose connection or a leaking gasket at the water outlet. It could also be a leaking hose.
A leaking heater core will cause the engine to overheat because the coolant is leaking out.
If your heater core is LEAKING engine coolant so that your engine coolant level drops too low or the engine coolant is lost completely and causes your engine to overheat then your engine can be damaged beside the mess the leaking coolant makes inside your vehicle ( you might be able to just temporarily bypass the heater core so that no engine coolant is flowing through the heater core )
The heater core has failed and is leaking engine coolant.